Incandescent electric lighting, already pushed to such a degree of
perfection in the details of construction and installation, continually
finds new exigencies that have to be satisfied. As it is more and more
firmly established, it has to provide for all the comforts of existence
by simple solutions of problems of the smaller class.
Take for example this case: Suppose a room, such as an office, lighted by
a single lamp. The filament breaks; the room becomes dark. The bell push
is not always within reach of the arm, and it is by haphazard that one
has to wander around in the dark. This is certainly an unpleasant
situation. The comfort we seek for in our houses is far from being
provided.
M. Clerc, the well known inventor of the sun lamp, has tried to overcome
troubles of this sort, and has attained a simple, elegant, and at the
same time cheap solution. The cut shows the arrangement. The apparatus is
connected at the points, BB', with the lighting circuit. The current
entering by the terminal, B', passes through the coils of a bobbin, S,
before reaching the points of attachment, a and b, of the lamp, L, the
normally working one. Thence the circuit runs to B. Within the coil, S,
is a small hollow cylinder, T, of thin sheet iron, which is raised
parallel with the axis of the bobbin during the passage of the current
through the latter. At its base the cylinder is prolonged into two little
rods, h and h', which plunge into two mercury cups, G and G'. The cut
shows that one of the cups, G', is connected to the terminal, B', and the
other, G, to the terminal, a', of the other lamp, L'. An inspection of
the cut shows just what ensues when an accident happens to the first lamp
while burning. The first circuit being broken at ab, the magnetizing
action of the current in the bobbin ceases, the cylinder, T, descends,
and the rods, h and h', dip into the mercury. It follows that the
current, always starting from the terminal, B', will by means of the
cups, G and G', pass through the lamp, L', to go by the original return
wire to B.
[Illustration]
The substitution of the lamp, L, for L' is almost instantaneous. It can
scarcely be perceived. It goes without saying that such an arrangement of
automatic commutation is applicable to lamps with two or more filaments
of which only one is to be lighted at a time. The apparatus costs little,
and can be made as ornamental as desired. No exaggeration is indulged in
if we pronounce it simple and ingenious. It may be used in a great
variety of eases. The diameter of the wire is 55/100 (22 mm.), its length
eighteen meters (60 feet), its resistance one ohm; ¾ ampere is needed to
work it, and less than a watt is absorbed by it.--_Electricite_.
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